Trencher teeth weigh generally in the range of about 5 to 10 pounds. These are installed on trencher machines and the buckets of small rubber tired and crawler tractors. Historically, these have been attached without the usual pin lock connecting the point and adapter. Instead, the adapter usually is equipped with a depression and the sidewalls of the point are heated and then deformed into a locking engagement with the adapter recess. It is not unusual for a changeover of points to take four hours, utilizing a welding truck to heat up the point. Normally, the welding truck comes out from the shop to go to the machine, then heats up the sides of the existing points whereupon the operator and his helper can drive them off. Thereafter, the new points are installed and after the sides are heated, they are dimple punches into the recesses in the adapter nose.
One effort to alleviate this time-consuming operation utilizing the welding truck is seen in co-owned U.S. Pat. No. 2,885,801 wherein the sides of the point were more malleable than the remainder of the point so as to facilitate dimpling. Nonetheless, vigorous manual labor was required for installation and removal. Another was to cast the dimples integrally with the hardened steel side walls, i.e., not using the malleable steel feature of the '801 patent. This was intended to provide a spring lock action. However, this did not perform satisfactorily inasmuch as negative thrust forces would pull the point off of its mounting adapter. Thereafter, the art uniformly has gone to the expedient of heating and peening the sides of the point into adapter recesses--to obtain a secure enough lock to avoid the unpredictable negative thrusts. For example, a stress tending to pull the point off the adapter may be encountered at any time the trencher moves rearwardly--as to position itself for a deeper cut. During this rearward movement, the point may become hooked on a rock, thus developing negative thrust.
The instant invention avoids all of the drawbacks of the prior art, particularly the deforming of point sides with its attendant hard physical labor by virtue of utilizing detent action in longitudinally extending tongues on the point or adapter cooperating with recesses in the companion element, viz., adapter or point, respectively, and in combination with helical thread means interconnecting the nose and socket of the two tooth elements. More particularly, the nose and socket arrangement is that shown and described in co-owned U.S. Pat. No. 4,335,532.
Teeth weighing 8 to 20 pounds are used on intermediate size rubber tired or track loaders. These typically have side locks usually of a steel and rubber sandwich design. The instant invention eliminates the need for separate lock costs and inventory and virtually eliminates the "knuckle busting" associated with installation and removal of side locks.
By the combination of the detent-like tongures which snap into companion recesses and the helical thread means interconnecting the nose and socket of the tooth elements, a point is now available which avoids the time consuming and laborious work of installation and removal. Now the imposition of negative thrust is incapable of pulling the point off the adapter because to do this, the removing force must also have a rotational component. More particularly, the detent means on the point and adapter is arranged and located to achieve locking engagement at the termination of the rotational movement of the point relative to the nose.
The invention also includes a novel means for securing the adapter element to the supporting portion of the excavator such as the bucket lip, etc. By virtue of utilizing uniquely contoured weld recesses in the confronting surfaces of the adapter, I am able to retain the adapter on its mounting irrespective of whether the weld fails or not--the unique contour developing an advantageous shear lock which prevents premature loss of the adapter. Welding, of course, has been used widely for many years in the securing of adapters to excavating machine lips and the like, as for example in U.S. Pat. No. 4,238,896. However, no one has appreciated the advantages of the contoured recess for establishing a continuous lock notwithstanding weld cracking.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.